1. Field of the Invention
The present invention relates to a bridge raising/supporting method for placing and replacing a bearing device to be sandwiched between an upper structure such as a bridge and a lower structure, and to the bearing device itself. More specifically, the present invention relates to a bridge raising/supporting method for placing a new bearing device even in such a narrow working site as could not replace the existing bearing device.
2. Description of the Prior Art
Between an upper structure (as will be called the "bridge") A such as a completed bridge or an express way supported by a bearing device and a lower support B supporting the bridge A, as shown in FIG. 15, there are sandwiched in proper positions a plurality of bearings C for transmitting a vertical load of the bridge A such as a dead load or an active load reliably to the lower structure B or for horizontally moving to absorb the extensions or contractions of the bridge A due to the temperature change and/or the horizontal movement due to earthquakes. These bearings C already placed (as will be called the "existing bearings") are often aged after a long time of years from the construction of the bridge A by the distortions due to the load or earthquake vibrations, the damages due to the bending stress, or the corrosions due to rain or sand to have their load absorbing function deteriorated or lost. If these existing bearings C are left as aged, they cannot absorb the individual loads upon the bridge A. As a result, the bridge A itself is often cracked or damaged and is broken down to cause a serious disaster. This danger makes it necessary to replace the aged existing bearings C by new ones.
In the prior art, the existing bearing C is replaced by the following method, as shown in FIG. 16. Near the existing bearing C, there are stacked metal plates or steel saddles to a level substantially equal to that of the existing bearing C to prepare a temporary support D. In the vicinity of the bearing C, there is placed a hydraulic jack E capable of raising the aforementioned bridge A while supporting it (as will be called "raising") to jack up (by several mm to 1 cm) the bridge A till the bridge A leaves the existing bearing C. Then, the bridge A is temporarily supported by a temporary bearing F made of several metal plates, and the existing bearing C is removed and replaced by a new one. After this, the bridge A is jacked up again to a level higher than the temporary bearing position to remove the temporary bearing F and is then jacked down. In addition to the method of replacing the bearing C described above, there are the known methods such as the bracket method or the special bed method to be adopted according to the conditions under which the bearing C is placed.
However, these methods cannot raise the bridge smoothly and still the worse require the works for placing the temporary supports D for the raising operations to elongate the term of works and raise the repair cost. In addition, the workers have to bear a heavy burden and a serious danger so that they are involved in an accident. Thus, we have invented a method of raising a bridge A or the like safely and easily and a device for use in the method, which has been patented and practiced, as disclosed in Japanese Patent Publication No. 54002/1992 or U.S. Pat. No. 4,944, 492. In the vicinity of the existing bearing C, as shown at (I) to (III) in FIG. 17, there is associated with pushing/pulling means 200 a wedge-shaped drive member 201 which has upper and lower sloped faces and which is sandwiched between two wedge-shaped pressure receiving members 202 and 203. As the wedge-shaped drive member 201 is pushed in the longitudinal direction by a hydraulic jack device 204, the wedge-shaped drive member 201 slides upward on the slope of the lower wedge-shaped pressure receiving member 203, as shown at (II) in FIG. 17, whereas the upper wedge-shaped pressure receiving member 202 slides upward on the slope of the wedge-shaped drive member 201 to raise the bridge A. In order to keep this state, moreover, a suitable number of horseshoe-shaped plate stopper members 207 are fitted across a sliding rod 206 of the jack device 204 in the space which is formed between a reaction receiving plate 205 of the hydraulic jack device 204 and the wedge-shaped drive member 201 to occupy the space thereby to regulate the movement of the wedge-shaped drive member 201 temporarily. In this meanwhile, the existing bearing C is repaired or replaced by the not-shown new bearing C'. After these series of works, the wedge-shaped drive member 201 is pulled in the longitudinal direction, as shown at (III) in Fig, 17, to lower the bridge A, thus ending the repairing or replacing works. Incidentally, during these repairing or replacing works of the existing bearing C, the bridge A is to be displaced or vibrated by the various fluctuating loads resulting from the traffic of vehicles, but these loads are absorbed by a slide plate 208, which is sandwiched between the upper wedge-shaped pressure receiving member 202 and the lower face of the bridge A, and by the not-shown shock absorbing plate. According to these method and device, the repair or replacement of the existing bearing C, which has been dangerous or impossible in the prior art, can be carried out safely and easily within a short time, as evaluated by those in the civil engineering and construction fields.
Our raising method and device have seemed to succeed in solving all the problems of the repairing or replacing works of the existing bearing. Although the method and device are effective in raising the bridge safely and smoothly, the hydraulic jack device 204 has to be left as attached, although unnecessary after the stopper members 207 have been fitted, so that the method and device are seriously wasteful.
On the other hand, the place for the existing bearing in the actual working site is various and beyond expectations. For example, some existing bearing C may have no working space for repairing or replacing itself. This seems to be caused by the fact that the construction of the bridge A at the early stage has taken no consideration into the necessity for providing the vicinity of the existing bearing C with a sufficient working space for the removal because the bridge A is placed on the bearings C set. The existing bearing C set on the follow-slam bridge or the like, as shown in FIG. 18, has little working space in the vicinity thereof, i.e., above the lower structure so that it may not be removed. Due to the damage such as the aging or buckling of the existing bearing C, moreover, the bridge A may sink from its initial reference position toward the lower structure B to narrow the gap between the lower structure B and the bridge A. In the worst case, not only the working space but also such a small space as to keep the existing bearing C out of touch may not be left. Especially in the concrete bridge, the problem is more serious because the gap between the lower face of the bridge A and the upper face of the lower structure B is designed to be narrow.
More specifically, our raising method and device described above is superior to the well-known method in that the bridge A can be raised safely and smoothly by inserting the raising device having a small height into the gap between the bridge A and the lower structure B. However, there is left and shared with the known method a problem in that the existing bearing C is repaired or replaced while the bridge A is being raised and supported. Specifically, in order to repair or replace the existing bearing C, there is necessary at least a working space S, as indicated by broken lines in FIG. 19. Thus, the aforementioned case cannot perform the repair or replacement of the existing bearing C physically because of no working space S for removing the existing bearing C. Of course, it is necessary not only to replace the existing bearing C but also to return the level of the sunk bridge A to the initial position. If, however, the existing bearing C is left as it is, the bridge A itself may collapse before long to invite a serious disaster as the existing bearing C breaks. Thus, what is taken is to replace the existing bearing C by the conventional method using the temporary support D, as shown in FIG. 16, or by lifting the bridge A itself by a large-sized crane, or to renew the bridge A and the lower structure B by large-scale works.
Therefore, we have made elaborate investigations and conceived the possibility of placing a new bearing even if no working space is left for replacing the existing bearing C, while abandoning the concept of the conventional method of repairing or removing the existing bearing C and replacing it by a new one by raising the bridge A. Thus, we have solved all the problems of the prior art by changing the concept into that the bearing itself has a function to raise the bridge while introducing the reaction and to stand for a long time while raising and supporting the bridge.